Composite adhesive and process of making same



Patented Feb. 21, 1928.

UNITED STAT ES PATENT OFFICE.

FRANCIS G. OKIE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO MINNESOTAMINING & MANUFACTURING COMPANYX OF ST. PAUL, MINNESOTA, A CORPORA- TIONOF MINNESOTA.

COMPOSITE ADIIESIVE AND PROCESS OF MAKING SAME.

No-Drawing.

thereof, have a wider field of utility.

Composite structures of the abrasive type such as sandpaper or emerycloth comprise generally (a) a backing of sheet material, which may befelted as in the case of paper or woven as in the case of cloth, (6) amore or less finely comminuted resistant material having abradingproperties. such as garnet or corundum, and (c) a binder generally inthe form of a glue which serves to bind the abrasive to the backing.

"The binders as produced at present have as incidents certain featuresamong which are (1) defect of desired drying qualities, (2) aflinity formoisture rendering them substantially inutile in the presence of wateror moisture, (3) the tendency to premature pulverization ordisintegration of the binder when exposed to normal atmosphericconditions and other undesired drying qualities, and (6) cracking, withconsequent exposure of the base, when bent.

The principal objects of my present invention are the provision of abinder which functions more efiicientlythan any known to me; theprovision of a binder characterized by flexibility without cracking orother undesirable effects; the provision of a bindor characterized byextensibility and coin; pressibility to accommodate itself to fiexion ofthe backingrthe provision of a binder by means of which the desiredadhesive action between it and the backing is attained not onlyefficiently but also with a desirable degree of acceleration, and moreparticularly the provision of a binder in which the drying action willbe effective from the contact surface between it and the backingoutwardly; the provision of a binder in which Application filed March 4,1922. 'serial No. 541,249.

the drying action will be effective from the outer surface thereofinwardly; the provision of a binder characterized by a drying actionthat permits of handling the product with a minimum of delay and moreparticularly such handling without impairment of the su'perficies of thematerial; the provision of a binder characterized by an accelerateddrying action; the provision of a binder the rate of speed of whosedrying is subject to variation; and the rovision of a binder havingmoisture-proo ng functions.

In the employment of my present invention for the production ofsand-paper and the like (which I cite for purposes of example) I use asthe backing a. sheet of material (which may be paper) as willconveniently serve the employment contemplated. and as the abrasive suchcomminuted material (which may be crushed garnet) similarly adaptedtoserve the function in view.

It is desirable that the binder utilized have the functions andcharacteristics not only of great mechanical strength and of greatbinding strength. but also that it be non-hygroscopic, permeative,moisture resistant, easily worked. readily obtainable, in-

expensive and facilely applied.

I have discovered that resins including some ,which are commonly calledgums of such types as are used in the manufacture of the better gradesof varnish are peculiarly adapted for the attainment of these ends andthat resins such as kauri, copal, dammar are examples of these types.preferred by me as best attaining the desired ends, viewed fromcertainaspects. In preparing the binder for use. the resin is used inconnection with a suitable vehicle which I prefer is of a type such aslinseed oil or China wood oil, for reason which I will proceed toexplain.

In applying a resin prepared with a vehicle such as linseed oil to onesurface of a backing of pa er for example I have found that the actionof the vehicle involves a penetration of the backing by the vehicle, forexample linseed oil, to a point which approximates the opposite surfaceof the sheet but falls short of actual exudation of the vehicle uponsuch opposite surface there Gum dammar is by preventing starving of thejoint between This results in a moisture-proofing of the material evenagainst the absorption of moisture through the surface opposite to thatto which the binder is applied, without at the same time defacingorotherwise undesirably affecting such opposite surface.

This penetration by the vehicle, particularly when coupled with the useof the character of resin pointed out above, carries with it in suchpenetration a certain amount of fine- 1y divided resin so that a coatingand binding action is secured between the fibres or elemental portionsof the backing which thus substantially retards, if it does not entirelyprevent, disintegration of the backing, in

.addition to preventing access of moisture through the backing to theplane of contact between the backing and the main mass of the bindermaterial.

The efficient action of the binder may be enhanced in the manufacture ofsand-paper if the binder is applied to the backing by the use ofpressure and the more or less finely divided abrasive is then applied insuch a manner as to cause it to adhere to the binder.

In order to accelerate the adhesion between the binder and the backing,I have ers generally, difficulties are encountered in handling theabrasive structure, within a convenient period because of the soft andsticky character particularly of the exposed surfaces of the binder.This objection I mitigate by associating with the improved binder asubstance the action of which is to produce an accelerated drying actioneffective primarily at the exposed surface and working inwardly, and forthis purpose I incorporate in the binder a. modifying element peculiarlyeffective in its action as an oxidizing agent on such vehicles aslinseed oil and as a retarding agent with reference to the excessabsorption of the vehicle by the backing.

The substance I have discovered to be particularly adapted for thispurpose is carbonate of lead or white lead which is a new electrolyticprocess white lead and which in my experience is found to be moresatisfactory than any other known form ofcarbonate of lead.- I

' Whereas by itself "the aforementioned white lead adds but relativelylittle strength to thebinder, in association in the binder withtheborate of manganese it intensifies the action of the binder in holdingthe abrasive firmly against the backing.

For increasing the adhesive properties of the binder, and for hasteningthe drying thereof, I have discovered that it is desirable to employ apaste dryer (ed-called because it is formed in the nature of a paste)which is also efficacious in holding the mineral particles such as gritin suspension in the binder without loss of siccative properties andwithout appreciably reducing the desired fluidity -of the binder. Thismay comprise such metallic compounds as sugar of lead and borate ofmanganese suspended in a suitable vehicle such, for instance, as linseedoil or linseed oil with. a resin, but I find it preferable to form thepaste dryer so as to have the metallic compounds contained therein inthe form of acetate of lead and resinate of manganese. I have found byexperience that the paste dryer should be somewhat in the nature ofcheesy butter, rather softer, and of a light brownish grey color.

As an auxiliary in (1) accentuating the adhesion of the binder to thepaper, (2) facilitating to a certain extent the spreading of the binder,and (3) modifying as desired the consistency of the binder as is usefillin cases where it is desired to render it more fluid, I have discoveredthat the use of a japan dryer is desirable. Such a dryer which isrelatively free from rosin is to be preferred. One form of this containsshellac, red-lead, litharge, manganese oxid, burnt umber, resin, linseedoil, and turpentine quantum sufiicit.

In order to give thebinder the desired fluidity, viscosity and bulk Ipreferably employ a varnish consisting largely of linseed oil boileduntil it reaches nearly a solid state.

As far as practicable and feasible uncombined' fatty acids and glycerinshould be eliminated. I have employed a linseed oil successfully forthis purpose having an iodine number as low as 185, but refer that ofhaving an iodine number as high as 190.

The aforementioned resins, such as gum dammar are preferably employed inthe form of a varnish which is substantially three parts Batavia dammar,steam kettle melted, with two parts kettle boiled linseed oil.

While gum co al and gum kauri in cer-' tain respects ma e moresubstantial binders than gum dammar, as they will carry more I oil anddry harder under certain conditions as may be useful for certainpurposes, gen-' erally speaking th'epresent relatively greater expensedoes not ordinarily justify their use for most purposes, which are wellserved by gum dammar.

Though I have hereinabove disclosed cercharacteristics, and likewise,Lhave discovered that where it is advisable that the siccati ve actionthereof be limited, or at least retarded, that it is desirable toincorporate in the binder a non-drying oil such as castor oil or thelike, for suc purposes.

"sandpaper'made in accordance with the disclosure of n y presentinvention is characterized by great flexibility without any adfverseeffects, such as cracking of the binder or backing, or loosening of onefrom the other'.

In my preferred practice, as will hereafter appearQI form batches whichbyweight and percentage j contain the" following ingredi-, ents:"

Lbs.

" Carbonate of ]ead l .1066

smooth."

J the composite batch is then milled until Parts I and II include thegum varnish in order to? attain not only a'fine subdivision ofthemetallic substance but also to render them readily miscible with PartIII.-

The materials'used by meas hereinabove described may be varied incharacter so as to 4D .var yfthe characteristics-of the binder from Ithe stand-point 10f adhesiveness, xion-hygro:

,' scopy, and flexibility." Wheresuchvariation' in ,the use of materialsis emp'l'oyed to produce, for instance, "increased adhesion be-' creasemay be attained though oss'ibly at a jcerta'inexpensein itscharacteristic of flexibility,

H san -paper characterized by extraordinary tweenthe binder and theabrasive, such inthis process, I am enabled to obtain thinness andflexibility, in that I am able to Q Inthe preferred practive of myinvention,

I I form sand-paper and the like witha backing Sdthln that such productcould not be manufactured, 1f the backing originally used were of thethinness ultimately desired.

in forming Part I hereinabove referred to, I grmd the carbonate of. leadand the gum varnish to an exceedingfineness which may be accomplished,by passing them through a fine-grmdmg mill three or. four trips. Theomaterlal grinds quickly and easily and may be conveniently mixedjin themill. One of thefuncti'ons ofthe carbonate of lead'is to hasten theoxidization of the thinner (and and 'ingal Ycalled gums,

greasier) elements of the binder and limit or the like, rendering itamong other t ings easier to handle before it becomes dry. Or

dinary white leads, even though of apparent equal purity and of similaranalyses as that herein referred to, do notj unction as satisfactorilyfor chemical reasons not yet brought to light by my experience.

Gum varnish may be No. 1 gum kauri, gum copal, or gum dammar or more orless numerous similar suitable resins commonly called gums meltedin'boiled or raw linseed oil, with or without the presence of dryers,suchasred lead, litharge, black oxid of manganese, burnt umber, and thelike. The gum varnish preferably used by me in Parts I, II. and IIIabove referred to, is substantially equal parts Batavia dammar gum,steam kettle melted, and kettle boiled linseed oil. While I preferablyuse gum dammar, as just indicated, I have formed a. um dammar varnishmade from three arts atavia dammar, melted by itself un er gentle heat,as is preferable thoughrit may be used cold, and two parts of ahydrocarbon (which maybe one of the etroleum series)obviously addedafter tile heat, if used, is discontinued. The hydrocarbon referred topreferably takes, the a following form Color, water white; Beaum, 4849;initial boiling point, not below 2759 .F.; not more than 50% over, at340 F.; recovery, at least 95%; residue, colorless; end point, below 475F. I

As the hydrocarbon evaporates, it may be advisable to add more to themixture in order to preserve the desired degree of fluidity. Thehydrocarbon dammar varnish thus formed makes a more brittle binder thanthe linseed oil gum dammar varnish above described. 1 Although gum copaland gum kauri each make a more substantial binder than um dammar, asthey carry more oil ry harder, the are more expensive. Gum dammar, thougnot oxidizing to such a degree of hardness and toughness as other gumsmentioned, is preferab e for my purpose because it ap roximates asnearly as ossible the desira le properties of kauri, ut a preaches incost rosin without includthe undesirable characteristics thereof andgoes as far in the direction of the employment of common rosin as I amat present advised is safe to do.

I have found that synthetic resins can also be used in place of naturalresins, sometimes to good advantage in making a binder for my purposes.-An example of sucha synthetic resln' is that known to the trade asbakelite resin, or commercial phenol resin produced by a condensationprocess. In using borate of manganese I have found that awell knownborate of manganese, readily obtainable in the open market combines bestsiccative properties with susceptibility to fine rinding and to formPart II referred to above it should be ground in the varnish until itmay be spread on a glass without being mealy under ones finger. Itshould be ground until experience shows that it can be ground no finer.

It will be understood from the foregoing reference to dryingintensifiers that the siccative properties of the borate of manganeseconstituent are such as to include facilitating drying outwardly of thebinder from the surface in contact with the backing, and that thecarbonate of" lead constituent includes causing drying inwardly of thebinder from the surface thereof which is in contact with.

the air. L

While I prefer to employ manganese compounds in the form of borate ofmanganese, it is to be observed that although black oxide of manganesecontains certain-desirable siccative elements for my purposes, it doesnot readily lend itself to grinding in such a manner as is desired byme. At times, advantage may be taken of the characteristics of blackoxide of manganese as a drier by heating it in linseed oil and usingthis mixture.

Similarly, cobalt derivatives, (such as me tate of cobalt) may beemployed for their siccative qualities, but I have found that due careshould be employed in using such highly concentrated dryers so as toavoid any tendency toward deterioration and relative inactivity with theother dryers; failing such care such cobalt derivatives do not give suchexcellent effects as borate of manganese.

In forming Part II accordin to my pre ferred practice, I find itdesirable to grind the borate of manganese by itself, ten or twelvetrips if necessary, as this is relatively a very hard substance togrind, and the varnish may be mixed therewith in the mill.

The form of japan-dryer preferably employed by me is a well-known japanwhich contains about 2% (two percentum) of shellac, preferably the bestobtainable, besides substances such as red lead (Pb O litharge PbO)manganeseoxid (MnO) burnt umber which has a manganese and oxygen con-- 7tent) and resins in linseed oil and turpentine. It aids in the bindingaction and acts to some extent as a thinner whose turpentine contentevaporates after the binder is spread on the paper and somewhatfacilitates the spreading process. I have the pro portion of japan dryerindicated in Part III as ordlnarily adequate but yet capable of increasewith safety when larger quantities are desirable. Although to anunaccustomed observer a rosin content in the japan may, due to itsrapidity of action, appear to be advantageous, such a content, is withinmy experience undesirable, and to. be avoided.

solid. While this is more difiicult to handle,

I find that it possesses to a high degree the ideal balance betweenfatty acids and glycerides, so that it neither overoxidizes nor does itdry sticky.

In preparing the paste-dryer of Part III above referred to, whichpreferably incorporates two separately prepared compositions, I firstform the initial portion of the dryer by stirring 200 pounds of litharge(PhD) and 200 pounds of hot water (120 F.), the agitation of the waterbeing sufliciently violent .during and after the addition of thelitharge to keep it from settling. After, say, two to five minutes ofthis sustained. agitation, 45 pounds of 80% acetic acid is dashed intothe hot-water and litharge composition without cessation of the violentstirring, which may be mechanical agitation, and which should continueuntil the milky white liquid that develops as soon as the acid strikesthe waterand litharge, sets to a consistency resembling soft cottagecheese or bonny clabber and offers resistance enough to tend to slow upa strong man using a paddle.

In cases where a mechanical agitator'is used, it should be shut off atthis stage which is ordinarily reached within a minute after the aceticacid is dashed in. It is advisable to have the agitation sufiicicntlyviolent to cause suspension of all of the litharge and to dash in theacetic acid suddenly, as otherwise a quantity of uncombined lithargewill be found at the bottom of the mixer, and the mass, which-is nowbasic acetate of lead. will not set stifi. This resultant Inass shouldbe undisturbed for about 15 hours and then pounds kettle boiled linseedoil is added to the mass, which by. this time has become somewhatstiffer. The whole mass is then mixed preferably in a mechanical mixer.The mixer should be run until a large percentage of the original watermay be poured off. At this time the basic acetate of lead has a greaterafiinity for the oil than for the water. When further agitationseparates out no more water, the compound should be ground. This may bedone on 3 roller ink mill until no more water can be discerned, and whensubstantially all ofit can be accounted for by weighing the water thathas beenpoured off. The strength of the acetic acid may be varied belowprovidedthe proportionsare changed correspondingly to the strength ofthe acetic acid. This forms the first part or composition of the pastedryer.

While the second part of the paste dryer I mix thoroughly 100 pounds ofkettle boiled linseed oil, with 75 pounds of. resinate of manganese(powdered form) and then grind the mixture two or three trips until fineand smooth.

I then add 225 pounds kettle boiled linseed oil to the acetic acidtreated litharge formed in the mixer as above set forth, and thenouicklv mix the resulting mass of the second resinate manganesecomposition with the modified first or lead compound ortion by resinateof manganese; then certain modilication of the portion A is affordedtojget AC; namely, adding linseed oil to the part A. When this isaccomplished I add AC to B and thus obtain the complete mixture D.

This mixing of the two'portions should be done quickly because there isa nicely balanced proportion between the two, and an excess of eitherportion in long contact with the other portion, imperfectly mixed,causes a livering and sometimes a separation therebetween. After thismixture of the two portions has stood for substantially an hour, theyshould be'milled one trip. This completes the paste dryer. It shouldflow down the apron-of the mill about one inch deep, (more or less,depending partly on tightness of rollers and consequent heat,) and itshould be kept in stock in a consistency about like cheesy butter, butrather softer,

pro erties.

and of a light brownish gray color.

The manganese compoundmay be'made from a resin other than rosin Wl'llCllfor my purpose may be dammar, kauri or similar compounds which inthepaste drier will in the final product render the same more tenacious,stable and of augmented physical rom the foregoin a parent that one othe general functions 0? the carbonate of lead is to serve primarily asa filler; and of the borate of manganese as well as of the japancomposition referre to, is toserve primarily as a dryer, and that therest of my improved binder is made up of varnishes.

The gross formula of the binder produced b my method considered fromthis'ust re- 0! ed aspect of the invention, there ore involves the use,generally, of four parts filler three arts dryer, and seventeen partsvarnish, referably associated together in the specific manner set forth.

The binder is formed, in my preferred practice, by runnin togetherthrough the mill Parts I and I ound finel as de- 05 scribed, togetherwith t e items of art III,

description it will be all three parts being milled together until thewhole mass is uniform and smooth. The

binder thus formed should be kept carefully covered preferably incontact with oiled paper to prevent the formation of surface skinthrough exposure. Having thus described my invention and illustrated itsuse, what I claim as new and desire to secure by Letters Patent is- 1.The process of producing a binder for sandpaper which includes admixinglead carbonate as an oxidizing agent with a varnish, combinmg the samewith a varnlsh ineluding a compound of manganese as a siccativeandadding a drying oil and a drier thereto, whereby the whole is adapted toharden or congeal into a substantially stable, flexible form orcondition for forming a coating which will adhere both to the supportingbacking and abrasive particles.

2. The "process of producing a binder for sandpaper whichincludesadmixing a com,

pound of a heavy metal as "an oxidizing agent with varnish,'combiningthe same with a varnish including a compound of manganese, adding adrier and linseed oil varnish, whereby the whole is adapted to harden orcongeal into a substantially stable, flexible form or condition forforming a coating which will adhere both to the supporting backin andabrasive particles. V g',

3. T e process of producing a binder for sandpaper which includesadmixing a compound of a heavy metal as an oxidizing agent with a gumvarnish, combining the same withlinseedoil including a drier and addinga varnish including linseed oil, a resinate of manganese and basicacetate of lead,

whereby the whole is adapted to harden or congeal into a substantiallystable, flexible form or condition for forming a coating which willadhere both to the supporting backin and abrasive particles.

4. T e process of producing a binder for sandpaper which includesadmixing lead carbonate with a gum varnish, combining the same with agum varnish including a siccative and with linseed oil varnish togetherwith the reaction product of basic lead acet ate and resinate ofmanganese whereby the a substantially stable, flexible form or conditionfor forming a coating which will adhere both to the supporting backingand abrasive particles. r

5. The process of producing a binder for sandpaper which includespreliminarily forming individual batches of varnish eac includingrespectively, a compound of a heavy metal as an oxidizing agent, asiccative, and a paste drier comprising the reaction product of basiclead acetate and manganese resinate, combining said batches ada ted toharden or congeal into a substantia y stable,

whole is adapted to harden or congeal into sandpaper which lncludesadmixin form or conditionfor forming a coating which will adhere both tothe supporting backing and abrasive particles.

6. The process of producing a binder for sandpaper which includespreliminarily forming individual batches of varnish,'eac of said batchesincluding, respectively, a filler having oxidizing properties and asiccative, combining said batches, then adding a linseed oil varnishwhereby the whole is adapted to harden or congeal in a substantiallystable or flexible form or condition for forming a coating which willadhere both to the supporting backing and abrasive particles. v

7. In the process of preparing a binder for sandpaper including a gumvarnish, the step which includes preparing a basic acetate of lead in anaqueous medium and separating the basic acetate of lead from the mevdium in which it is formed by the addition thereto of a vehicle solublein the varnish.

8. The process of producing a binder for lead carbonate with a varnishtherefor com ining the same with a varnish material including borate ofmanganese, adding a paste drier including the reaction product of basicacetate of lead and a resinate in linseed oil whereby a composition isobtained adapted to form a substantially stable, flexible coating whichwill adhere both to the supporting backing and abrasive particles.

' 9. The process of making a binder including metallic compounds servingas a filler and an oxidizer, gum, varnish, linseed oil varnish and adrier which includes the steps of preparing individual batches of saidcomadhere both to the supporting backing and abrasive particles.

10. The process of producing a binder for sandpaper which includescombining with a gum varnish, a mixture comprising a powdered, bodyaugmenting agent in a vehicle soluble in the varnish and lneluding' agum, adding a drier thereto and an additional quantity of gum varnish,whereby the whole is adapted to harden or congeal into a substantiallystable, flexible form or condition for forming a coating which willadhere both to the supporting backing and abrasive particles. l

11. The process of producing a binder for sandpaper which includescombining with an oil varnish, a mixture comprising a normally dry,powdered body augmenting a cut in a vehicle soluble in said varnish, ading a drier thereto and an additional quantity of a drying oil varnishwhereby the whole is adapted to harden or eongeal in a substantiallystable, flexible form or condition for forming a coating which willadhere both to the supporting backing and abrasive par-- tieles.

signed my name.

FRANCIS G. OKIE.

